


Mercy

by DadIWriteGayPorn



Category: Big Hero 6 (2014)
Genre: Accidental Voyeurism, Alpha Tadashi Hamada, Alpha/Beta/Omega Dynamics, Anal Sex, Bathroom Sex, Brother/Brother Incest, Come Shot, Condoms, Content approved by SCAR, Dead Dove: Do Not Eat, Exhibitionism, Frottage, High School, Loss of Virginity, M/M, Mating Cycles/In Heat, Non-Traditional Alpha/Beta/Omega Dynamics, Omega Hiro Hamada, Peradynamics, Public Nudity, References to Knotting, Semi-Public Sex, Sleeping Together, Trans dynamic, Virginity, first heat, heat supressants, school sex, slick, slick pad
Language: English
Status: In-Progress
Published: 2020-09-07
Updated: 2021-02-08
Packaged: 2021-03-06 23:34:34
Rating: Explicit
Warnings: Underage
Chapters: 3
Words: 14,115
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26337277
Author URL: https://archiveofourown.org/users/DadIWriteGayPorn/pseuds/DadIWriteGayPorn
Summary: As Hiro goes into his very first heat, Tadashi must take on a responsibility he never dreamed of while trying to keep his little brother safe from another prowling Alpha
Relationships: Hiro Hamada/Tadashi Hamada
Comments: 10
Kudos: 119
Collections: Hidashi Hamadacest and Tadahiro, Sin Corps, only brothers (until they weren't)





	1. A Victim Of The Heatwave

**Author's Note:**

> This was quite the undertaking. Before starting this I'd only read 3 or 4 ABO fics, none of which had more than 3 chapters (honestly a travesty). But I was hooked! It has soooooo many kinks I love. I decided I wanted to try my hand. Then I learned just how expansive and intricate the Omegaverse is. It was too much to take in all at once and several things were contrary to the vision I had in mind in this fic. So while you'll recognize quite a lot here, this fic has it's fair share of tropes, I'll probably get a bunch of stuff wrong and leave a bunch out. I've decided I'm doing this my way., with my ABO vision I hope you enjoy it anyway and give it a chance!

The knock on the classroom door was so soft and hesitant Tadashi almost didn't look up. He was supposed to be taking a geometry quiz, but his mind had been drifting. The room was quiet save for the rustling of paper and scratching of pencils, and it was quite warm. Tadashi was doomed to get lost in his own blissfully empty head the second he'd started tapping his pencil in rhythm on his desktop.

But his attention was caught when their middle-aged teacher, Ms. Davidge, stood and made her way to the door. Tadashi watched her rear as she went, eyes drawn to her movement. He wasn't remotely into her or anything. He was just too lazy to lift his eyes up. She wasn't his type even without being more than twice his age and a girl. Plus, she was a Beta. All their teachers were, as a requirement. The last thing the school board wanted was Omega teachers in their heat hooking up with Alpha students like Tadashi, or Alpha teachers in their rut getting with Omega students like...

"Hiro?!"

Tadashi blushed when he realized he'd spoken out loud. Ms. Davidge had opened the classroom door to reveal his little brother standing in the hall, looking embarrassed and apologetic. His shoulders were hunched, his head hung low. He was wearing a nervous half smile that looked more scared than pleased. He looked like he wanted to lay on the tile floor, curl up, and not be seen.

Hiro raised his right hand and wiggled his fingers in a sheepish greeting.

"H-hey! Um, sorry," he turned to the teacher. "I need to check my brother out. Uh, out of class, I mean..." He looked down at his shoes and his perpetually messy black hair fell over his eyes.

"What's this about?" Ms. Davidge asked, peering down.

"Important family stuff," Hiro said, grabbing his wrist awkwardly when he realized he didn't know what to do with his hanging hands. "Please, it'll just take a few minutes."

The teacher turned to look at Tadashi and nodded. Mystified, Tadashi stood. He left all his things and began to navigate down the aisle towards the door. None of the other students seemed interested in this.

Tadashi tried to catch Hiro's eye so he could silently search for a hint as to what this was about, but Hiro kept his eyes averted until Tadashi was standing there next to him.

"Class ends in 25 minutes, Mr. Hamada," Davidge said. "I don't allow makeup examinations, except in extreme circumstances. If you aren't back to complete your assignment before the bell, then whatever progress you've made is final."

Tadashi gulped. That didn't bode well. He'd only answered three or four of the problems. But before he could dwell too much on that, Hiro snatched his hand and thanked the teacher huffily, then turned and started leading (or dragging, more like) his older brother down the hall. The door closed behind them. With a click that sounded forebodingly final.

It was always weird whenever Tadashi even saw his little brother in these high school halls. Tadashi was a senior himself and Hiro was 5 years younger. But Hiro was a genius, even at just 13. He'd skipped through most of middle school and was on-track to do the same here. But after 3 years here without him, Tadashi wasn't used to his sudden, distractingly young presence.

"Hey, hold on," Tadashi demanded. "Where are we going?"

Hiro just tugged at his hand and sped up. They rounded a corner and came face to face with two bathroom doors.

"Here," Hiro said, heading for the men's. He'd barely opened the door, however, before he reeled back.

"S-someone is already in there!" He turned on heel. Tadashi let go of his hand and crossed his arms.

"How can you even tell? You didn't even let the door open all the way."

"I... I just can, okay?" His voice cracked on the last word and he gestured with his head down the hall. "Can we please just f-find somewhere private? I know another place." He started off down the hall without waiting for an answer.

"Hey! Why does that matter?" Tadashi followed. He gave Hiro another once-over. Something felt different, not just with how his little brother was acting, but he had no idea what it was. He smelled the same, looked the same (if a little unkempt), and felt the same. But there was a sort of uncanny valley to him, like he was draped in a mirage or illusion.

"Please, I'll tell you everything when we're alone. Don't make me open up in the fucking hallway!"

"Language!" Tadashi snapped. "That's a dollar for the jar at home."

"Hurry up and I'll put ten in!" Hiro grumbled. He thrust his hands in the front pockets of his navy blue hoodie and kneaded them restlessly.

They entered the cafeteria. It was all shut down now, lunch having finished an hour ago. Hiro crossed it without looking back to see if Tadashi was following. A couple of the leftover lunch people who were wiping down tables eyeds the two brothers and Hiro hastily lifted his hood before plunging his small hands back into his pockets.

Two halls later and there'd arrived. A solitary bathroom door with the outline of a person on the front, half masculine and half feminine.

"You can't be serious? Here?"

Hiro nodded. "It's almost always empty about now. I don't think anyone's in there, anyway."

"Yeah, but this is the-" Tadashi stopped himself. Hiro finally looked up and met his eyes.

"It's the what? Say it."

"Uhm, gender neutral?" Tadashi tried, unconvincingly. Hiro shook his head.

"Unbelievable."

Tadashi didn't have prejudices. Not really. He liked boys, after all, and he tried to stick with a mindset of 'if someone wants to do something that doesn't hurt others, let them.'

But some of the jokes other seniors, especially Alphas, passed around had rubbed off on him. One in particular. That the men's restrooms were for Alphas and Betas, the women's for Omegas (and yes, Tadashi knew how fucked up that was), and this gender neutral one was for Peras, which was what Tadashi had almost said.

He didn't mean to be insensitive. After all, he fully supported trans people, and those engaged in Peradynamics were operating on the same lines. But Tadashi only knew one Pera, and their time together was aggravating to say the least. He knew that wasn't indicative of any of the rest, but that one little annoyance had still opened him up to so much of what his classmates joked about.

"Forget it," Hiro shook his head and grabbed his brother's hand again. "This is more important."

He kicked open the door and dragged Tadashi inside unceremoniously.

To Tadashi's surprise, it was actually fairly decent on the inside. At least, compared to the boy's bathroom. The tiles were more or less clean and there was no assaulting odor hanging in the air. Of course, it wasn't exactly glamorous either. It was _still_ A public restroom, with two urinals that had dividers and three stalls with locking doors.

Things were made even less glamorous when Hiro chose the third and final stall in the far corner of the room.

"Please, don't say anything. I know. Just... just sit."

Tadashi was more concerned than he was grossed out, so he did so without a word, settling down on the toilet seat, semi-impressed by the restraint of the binary-defiant students to not riddle the walls with graffiti, and hoping his brother wasn't about to tell him he'd killed someone or anything insane like that. Hiro closed and locked the stall door, then leaned against the wall for support, grimacing all of a sudden.

"Woah, hey, are you okay?!"

The boy nodded, holding his stomach and growling in the back of his throat. "Y-yeah! I've just been forcing myself to not react, to try not to feel it almost all day. I just need a sec."

"Not feel what? Are you sick? Was it that takeout we had last night? I know you didn't eat much, I saw you picking at it, but it only takes a little…"

Hiro didn't answer right away. It was less than a minute before he straightened back up. He quickly tore off his hoodie, revealing that he was wearing a plain black tank-top (an unusual choice for him, though Tadashi had to admit he pulled it off) and hung the jacket on the stall door. Tadashi stared at Hiro's thin, pale arms. In the stalls shadows what little peach fuzz he had on them turned invisible, making him look truly hairless.

Hiro finally spoke up.

"I don't really have a way to ease into this." He rubbed down the front of his shorts, grinding against his crotch, and Tadashi realized he'd been doing the same thing earlier with his hands in his jacket pockets. "So I'm… I'm just gonna say it, okay?"

"Hiro, you can tell me anything. If this is about your grades- I know you slipped in history because you went to a fight instead of writing that essay-"

"No, it's… not that simple."

"Tell me, Hiro." Tadashi took his brother's fretful hands and looked up at him, trying for an encouraging smile.

"I started my heat."

Tadashi blinked. At first he wasn't sure he'd heard right. Hiro had gone from seeming shy to matter-of-fact on a dime.

"You…?"

Hiro cleared his throat and repeated himself.

"Tadashi… I started my heat."

**Notes for the Chapter:**

> Chapter Title Inspiration- Heatwave by IAMX


	2. Melt In The Kiss

**Notes for the Chapter:**

> Sorry for the wait! This one is much longer and more detailed. Still leaving a couple of things vague, to be addressed in the next chapter or two. Hiro is actually fairly dominant here, despite bottoming. That will change over time, but considering Tadashi isn't rutting this chapter and is naturally caring and overprotective; while Hiro needs to be sated, it kind of worked out that way

Tadashi gaped at him. Everything clicked in his mind and made perfect sense, how Hiro had been picking fretfully at his food the night before, the uncanny valley in how he felt and smelled to Tadashi right now, the cramps the boy seemed to be experiencing... But he didn't want to believe it. Hiro was just so _young!_ Tadashi already worried more than enough over Hiro's safety when he would sneak off to Bot-Fights at night. But adding the danger of Hiro in heat, when other Alphas could smell him and take advantage?!

Tadashi let go of Hiro's hands so fast his brother flinched. He instantly regretted the move. If what Hiro had said was true then he was already on edge enough without the sudden movement and cutting-off of affection. 

"I shouldn't have said anything! You're my brother, I shouldn't talk about this stuff with you." Hiro turned to grab his jacket, a sour and hurt look on his face, but Tadashi stopped him, standing quickly. 

"Wait! I'm sorry! Of course you can talk to me about it. It's something natural, and it's new. You need someone you can go over it with. I didn't mean to hurt your feelings, it just surprised me. I don't smell it on you at all. You don't feel like you're in heat."

Hiro turned back to look at his brother. "I know. I took a suppressant pill last night before dinner, and one this morning first thing when I woke up. I recognized the signs from when you gave me The Talk last year. I didn't want anyone to notice. I thought I could get through it. I thought the pills would do more than just mask my scent."

"Y-you took suppressants?" Tadashi said, gulping to moisten his suddenly dry throat. He glanced down, trying to peek between his brother's legs, but saw no tell-tale damp spot from slick that would have left things without a doubt. 

Hiro nodded. "I thought it would help more," he repeated. "I thought it would make me feel things less, maybe even mute them for real, but all that's happened is it stifled my pheromones. Even without the scent I'm still feeling it all. The cramps, a bit of dizziness, all the slick I'm making... And the horniness. T-Tadashi, I haven't ever been this horny before!" He bit his lip, suddenly looking worried and pleading as he started rubbing his crotch again. 

Tadashi knew he had to be supportive, to give advice and help how he could, even with really small things. Cass was a Beta and wouldn't understand how powerful and frightening these cycle urges could be, and Hiro's admittedly few friends weren't the best of role models. But something else caught Tadashi's attention, set his senses tingling. 

"Where did you get suppressants from? They aren't free and you have to be 18 or with an adult to buy any."

Tadashi felt bad for asking almost straight away. It was an important question, but it wasn't what his brother needed right now. 

Hiro blushed a little. "K-Kyle gave them to me. He has a lot cuz of... Well, you know. He's still saving up for surgery and gave me a couple bottles of them from his surplus, just in case."

"When did _that_ happen?" 

Tadashi didn't mean for his question to come out all snappish like that, but he had his fair share of animosity for Hiro's unconventional friend. 

"About two months ago. He said he'd had his first heat at 14 and wanted me to be ready just in case. But that's not important! I need... I don't know what I need, but you can help."

"And I want to, Hiro. You deserve to be able to talk with me about this. But the best way I can help you is by getting you stabilized before we go over everything."

Hiro frowned. His hands rubbed at his crotch even more. Tadashi tried to ignore it, he knew his brother couldn't help what he was doing, but he kept impulsively glancing at it anyway.

"Why can't we talk now? I don't want to wait!"

Tadashi sighed. He leaned back and eyed his little brother, taking more details in. His cheeks were pink, as if he were standing in a chilly winter breeze. He was breathing through his mouth so his lips parted just enough to show off that adorable tooth gap. Hiro always showed it off when he was angling for something. Maybe it was unconscious, or maybe he knew how cute it made him look, how it made it hard to tell him 'no.'

"Because the side-effects of your heat don't only influence you, Hiro."

Tadashi wished Hiro would just accept that answer and go willingly. He was already exhausted from this day. He wasn't sure he had the spoons to play cat and mouse. And he needed to try and get back to class so he could do what he could on the rest of his exam. 

The cards just weren't on the table. 

"Your rut doesn't start for two more weeks!" Hiro licked his lips, maybe unconsciously, when he spoke the word 'rut.' "I'll be done with my heat by then."

Tadashi smiled ruefully, though it was only for Hiro's sake. "Even outside my rut- God, it's still weird talking about it- I can still be swayed. I'm only 17, I'm still going through changes of my own. So even without your heat pheromones or my rut hormones I still get horny. So do other boys, other Alphas and Betas, and they're not all as nice as me. If they knew... It's just not sustainable."

Hiro looked him dead in the eyes. "Why would that be a bad thing? There's other, more effective ways than suppressants to get through my heat."

At first, Tadashi didn't make the personal connection that Hiro was talking about him. He was so tired and concerned. His brain slipped over that crucial piece of information and made its own conclusion. 

"Hiro, I'm not going to let anyone touch you when you're in heat. Friend or stranger. When you're older if you want to get through your heat with someone the traditional way, that's fine. But right now you're 13! I can't let you risk getting hurt by someone."

"Do you plan on hurting me? Why not just embrace it?!" His eyes were wide, hinting, and hopeful. And this time there was no naively mistaking his meaning. 

"I... Hiro, you can't be thinking... We're brothers! We should at least try and keep things safe, yeah? I don't want to take advantage of you or be taken advantage of."

Tadashi wanted to stand, to get out of that confined place. He kept looking down at Hiro's crotch, at his bare arms, at his collarbone and boy's neck still hiding his Adam's Apple. He didn't want to want what his brother was suggesting, and was about to take his leave before he slipped up, but Hiro pressed forward, stepping between Tadashi's legs (he really should have crossed them) and grabbed his shoulder. 

"So what? It's not unheard of. You'd just be helping me through it. It's not like we're bonded, or like we will. I don't even know how to. And you're not in your rut, yet."

His shorts had a definite bulge now. Tadashi stopped trying not to look. He couldn't believe this was happening. _Why isn't the idea of this making me sick? If I were rutting I'd understand, but I still have two weeks! This isn't right..._

He had to try and spurn Hiro's advances. He'd taken a class on this a few months earlier. He couldn't physically rebuff him. There was a chance Hiro could get hurt, and when Alphas restrained Omegas, the Omegas tended to become more pent up and ornery. No, he had to try and reason with him. It was so strange and unexpected coming from his little brother, though. He had to keep in mind that nothing Hiro said or did here was his fault; his body was betraying him. 

"Come on Hiro, you know this isn't the right way. Let's... let's go talk to the school nurse."

"What can she do to help me?" Hiro snorted. "Aunt Cass is a Health & Safety certified Beta too, but last year you told me we wouldn't involve her in our puberty or cycle stuff. But I'm supposed to trust the nurse, who knows me less? Seriously, what can she do?"

"Not get you pregnant at thirteen for starters!" Tadashi exclaimed, his ears reddening defensively. This wasn't going as well as he'd hoped. Even in his heat, Hiro was smart as a whip. 

Hiro gave a fervent chuckle and swept some hair out of his face. Tadashi stared as Hiro's tank top was hitched up. 

_God, when he lifts his arms like that I can see his hip bones!_

He mentally slapped himself. 

"Is that what you're worried about?" Hiro's voice claimed Tadashi's attention again. "Pups? You're not rutting, so between us the chance of fertility evens out!" Hiro stepped around his brother's legs and sank down onto his lap. Tadashi yelped. _So much for that smart as a whip theory. Selective._

"Th-that's not how math works and you know it. I'm not on my cycle b-but you are. One plus two doesn't equal two."

Hiro shrugged. "Whatever. I don't care about that right now. I just... I _need_ this, 'Dashi! Please! They say heats are longer if you only use suppressants to get through them. And I'll still be pretty horny through it. And I could get sick! Please, this is the best way! If I don't have you, someone else will surely do."

"H-Hiro..." Tadashi found himself grabbing the boy's hips. His palms were against the fabric of his shorts, but his fingertips brushed on bare skin above his waist and under his tank top. 

Hiro started to gyrate his hips, grinding on his brother's crotch. Tadashi groaned out, shocked and afraid when he started to stiffen up in response to the stimulation. 

"Was th-this your plan all along? Get me alone and g-get in my pants."

Hiro continued rolling his hips. "No... Maybe? I don't know." 

He let go of Tadashi's shoulders and grabbed both his brother's wrists. "If it's really pups you're worried about, I have a condom... In my back pocket..." He started to slide Tadashi's hands off his hips and around to his ass. 

"Where did you get condoms?!"

"Kyle," Hiro said simply as the hands rounded his curves. 

They both gasped as the hands went willingly into place on Hiro's butt. Tadashi surprised even himself when he didn't resist. 

_What is wrong with me?! I should be talking him out of this! We're almost to stuff we can't take back._

His brother's words repeated in his head. _"If I don't have you, someone else will surely do."_

There was no doubt in Tadashi's mind that Hiro meant it. And the last thing Tadashi wanted was for Hiro to find some other Alpha who probably wouldn't treat him right. And he knew from experience with Hiro sneaking out to Bot-Fights that he wouldn't be able to stop his little brother if Hiro's mind was made up. 

Tadashi's resolve crumbled away almost entirely. He started to squeeze Hiro's cheeks. Just a tiny bit at first, as if he were just trying it out, then more fully. They felt so perfect, even through two layers of clothing. That Goldilocks Zone of just enough fluff, firmness, and roundness. Tadashi went fully erect in his jeans. He muttered a quick _"fuuuucckkk me!"_ then with slow, trembling fingers he slipped the square condom out of his brother's back pocket. 

"I need you t-to meet me halfway... I help you out now, then we get you h-home and sort out how to deal w-with the rest if your heat, okay?"

Hiro tilted his head up, eyes fluttering shut, and sighed. "Y-yessssss! Thank you! Th-thank you! I knew I could get you to see it my way." He rubbed his butt down on Tadashi's crotch some more. This time he could feel his older brother's erection, which prompted him to grind harder. 

"You aren't even slick," Tadashi noted, a bit dubious. "Are you sure you-"

"Oh, I'm slick!" Hiro assured him, looking back down. "I'm just wearing a pad."

He took the condom package from Tadashi's hand and then moved them both again, this time sliding them around to his front and resting his brother's fingers on his shorts button. 

"Why don't you help me take it off? **All** of it. The pad and the clothes~"

"You've got a slick pad?" Tadashi hummed in the back of his throat. "You're doing better with this than you think. But where did you… no, let me guess. Kyle." 

Hiro gave a false pout. "What, are you jealous?"

"I just don't like the guy. People always tease us for looking alike but he's such an asshole and a slacker. I'm nothing like him."

Hiro leaned in close and whispered into his brother's ear. "I don't know… he's an Alpha, too. I think he's hot~ and since you look like him…"

"He looks like me!"

"Same difference. Just take the compliment." The boy chuckled a little, then nibbled briefly on Tadashi's earlobe, making him quake. "Now. Are you going to strip me or do I have to do it myself?"

"What, you can't give me a second to wrap my head around this?" Tadashi raised an eyebrow. 

Hiro shook his head, eyes glinting with mischief. "Nah, you might rethink it. Can't risk that!"

Tadashi stuck his tongue out, and Hiro returned it. But that little bit of teasing was enough to settle them both. It was like their regular quipping relationship, and that normalized Tadashi's anxiety. He was ready. 

Well, almost ready. He started to undo Hiro's front button, but quickly stopped. Something still didn't feel right. He sought around for what it was, but wasn't sure until he looked up into Hiro's face. The boy was sweating and glowing, his face tinged red. Tadashi should have seen these surface signs of Hiro's heat before now, but that didn't matter. His eyes locked onto every detail, from his brother's button nose to his hopeful brown eyes. 

"How… how have I never noticed before?"

Hiro frowned, obviously hoping they would hurry up and fuck. "Notice what?"

"Notice that you're. . . That. . . Hiro, you're _gorgeous!_ " Tadashi reached up and cupped his brother's right cheek. "I mean, I have noticed, but I've never taken notice, you know what I mean?"

Hiro flushed more and shook his head. "I.. I don't, uh… I mean, I don't look _that_ great. I always thought that my head was too big, my arms are too skinny. This tooth gap makes me look like a little boy," he parted his lips and stuck his tongue tip through it to illustrate his point, "and I'm so short! If I fluff my hair up then I juuuusstt make it to five f-"

He was cut off when Tadashi, smiling profoundly, pulled his brother's face forward and kissed him. It wasn't a deep kiss, or a fierce one. Just a gentle and loving touch of their lips that lasted a couple of seconds before his older brother pulled back. But it rendered Hiro momentarily speechless. His eyes went out of focus and he stared at the wall, the tiniest of grins lighting his features. He felt a warmth spread through his chest, quite different from the hotness he was already feeling all over. 

"Hiro, those things," Tadashi whispered, his hands returning to pop open his brother's button and slide down his zipper, "all of them, they're features, not bugs."

"My suppressant must be wearing off," Hiro giggled a little, then sighed as some of the pressure on his straining cock was relieved. "T-ten minutes ago you were talking about how to avoid getting swept up in me. And now you're kissing me, calling me gorgeous, and are gonna mate with me!"

Tadashi shook his head. "Not mating, I'm just helping. Alleviating. When I put myself inside you, your body is going to be sated. Not for long, but it'll help. Then I'm driving us home." 

"What about your exam?" Hiro slipped off Tadashi's lap and stood so they could get his bottoms off. "You're missing it"

"You're more important. I couldn't finish it now anyway. Besides, legally the school has to make allowances for students' cycles. I'll bet that overrules whatever personal classroom guidelines Davidge has."

Hiro rubbed the condom he was holding between his thumb and forefinger. It was in a bronze-colored packaging. Supposedly slick-reactant to increase Omega pleasure. Part of Hiro wished Tadashi would bareback him raw, and he almost asked him to. He would've used his most pleading, innocent voice paired with his best lip-trembling pout. But he held back. He understood why Tadashi was being cautious and he didn't want to risk breaking this spell and having Tadashi rescind his agreement. 

In any case, it was nearly too late for that. With Hiro's button popped and the zipper dropped the older boy only had to reach out and tug the bottoms down. He did so with steady hands, grabbing both the shorts and the underwear. 

"This is it... I'm about to see you naked... And hard... And more." 

"I want it, Aniki," Hiro told him. 

"Even though I'm your brother?"

"Can you think of an Alpha who would be better for me?"

Tadashi almost jokingly said 'Kyle,' but he swallowed it back. He couldn't even support that punk as a joke. Plus, he was starting to grow suspicious of his doppelgänger. But now wasn't the time. He swallowed, then snapped his eyes forward and started slipping Hiro's clothes off. 

Bare skin on his thighs revealed itself first. Then below his belly button. But with one determined tug Hiro's hard-on came into view. Both boys shuddered. Tadashi felt himself get even harder. So hard it ached! He wasn't supposed to see this part of his brother. His eyes weren't ever supposed to take in that four inch member.

Hiro's head was completely hidden by foreskin, even while hard. Tadashi could still make out the boy's corona outlined under the thin flesh, but it still looked odd compared to his own, ending in a sort of cone. It reminded him of stored furniture draped in sheets. 

But his brother's cock wasn't what Tadashi needed. He pulled the bottoms the rest of the way down. As Hiro kicked off his sneakers so he could step out of his clothes, Tadashi saw the pad. It was a long, almost plastic-like white strip that started behind the base of Hiro's small sack and traveled up between his butt cheeks and over his asshole. 

"Turn around," Tadashi instructed once Hiro was properly free from his bottoms. "And take off your tank top, too. No reason to keep it on at this point. It'll only get in the way."

Hiro didn't hesitate or question. He turned to face the stall door and tugged off his black tank top, dropping it to the floor. He stood before his older brother, fully nude and confident, though he was starting to shake from pent up horniness. He needed a dick inside him, and fast. 

Tadashi rose to his feet as well. His crotch was only an inch or two away from Hiro's ass. He discarded his shirt too, then unbuckled his belt and thrust down his jeans as quick as he could. The older boy's cock, mostly free, pointed forward and rubbed against Hiro's bare butt through its pitched underwear tent. They both groaned aloud and Tadashi slipped off his boxers and let his member plop against Hiro's cheeks.

Tadashi's cock was very different from his brother's. For one thing, he was around twice as large. A good eight inches or so. It had an ever-so-slight upward curve to the shaft, while Hiro's was straight as a dowsing rod. And Tadashi's foreskin only covered some of his tip, none once he started rubbing himself on Hiro and his crown flared a little. 

Tadashi stripped off his own shirt and wrapped his right arm around his little brother's chest, tugging him close. The skin of Tadashi's newly exposed chest pressed on that of Hiro's smooth back. He was amazed by how hot to the touch Hiro was. He'd known there was a reason why an Omega's heat was called a heat, but it was still a little jarring. 

Hiro whined and pushed his butt back. "Come on! You've been taking every step so slowly! Can't you just dive in already?" 

As if to illustrate Hiro's point, the school bell rang to signal the end of class. It startled Tadashi a little bit, making him twitch in surprise, but Hiro gave no outward sign he'd even heard it, though he must have. Tadashi knew there would be five minutes before the start of the next lesson, which they would both be skipping as after this Tadashi planned to drive Hiro home. He would need to be taken care of for the next two days at the very least, and they would have a **lot** to sort out. 

"I just want to enjoy this... And make sure I'm doing everything right." 

Tadashi reached with his free hand down around to Hiro's front and grabbed him gently by the balls, they were so small and round, and the movement Tadashi felt as he manipulated them could have entertained him for a solid hour. 

"Have you ever even been with an Omega?!" Hiro demanded. "Please, Tadashi, you c-can't go this slow!" his voice cracked. "I can't take it... You need to do _something!_ Please!" 

"Alright, alright... You promise you'll be oka-"

"TADASHI!" 

If he weren't so horny, Tadashi probably would have rolled his eyes. Instead, he slipped his fingers down past his little brother's sack, palming it, and got the tips under the pad. He pulled, and it came free with a wet schlopping sound. Tadashi felt the slick coating it soon enough. It was thicker than a lot of synthetic lubricants, but every bit as slimy, and was hot to the touch while most synthetic lubes were cold when they left the bottle. Tadashi tried not to get lost in the feeling and pulled the rest of the pad off before dropping it on top of their discarded clothes. 

And then the smell hit his nose. He had just been taking a normal, shallow breath, but it turned into a long, deep intake as he instinctively chased the scent. Hairs rose all over Tadashi's arms and legs. The smell was like a drug, a high Tadashi never knew he needed. It was the essence of sex itself, seemingly. All unsuppressed pheromones and the promise of his brother's insides. It took all of Tadashi's willpower down to the last minuscule drop to ask for the condom instead of thrusting himself unprotected and balls deep right off the bat. 

With a shiver, Hiro held the condom out behind him between a middle and pointer finger. Tadashi snatched it up and held himself back from ripping it open with his teeth as Hiro hastily placed both palms against the stall door, a hand on either side of this hanging jacket. 

Tadashi's fingers were shaking so badly he almost ripped the condom anyway as he peeled open the bronze packaging. He tossed the wrapper haphazardly aside, not caring when it drifted under the divider and landed on the floor of the neighboring stall. Quick as he could, the older boy rolled the thing down his shaft and grabbed Hiro's hips. 

"I still can't believe you talked me into this!"

Hiro almost snarled. "Like you don't want this too! Now I swear, if you keep trying to talk casually, or at all, instead of fucking me. . . I'm walking out of here bare naked and am gonna find my own Alpha."

Tadashi almost said "sorry." In fact, he wouldn't have caught himself if it wasn't for the hot spike of annoyance that rose from his belly. He knew his brother couldn't help it, but who was he to be so demanding and arrogant like that? He was the Omega here! He needed to be reminded. 

Tadashi didn't even line himself up properly. He just slipped the head of his cock between Hiro's cheeks and thrust forward. And it worked! Everything else lined up for him. Hiro was hairless, his butt curved perfectly, and he was bent forwards enough that, once the slick Hiro had produced coated the already somewhat lubed condom, Tadashi's cock slid on down the curved crevasse and drove right into Hiro's hole. 

Under any other circumstances this would have hurt Hiro enough that he would cry for Tadashi to stop and continue crying for a while after he did so. This was, presumably, Hiro's first time ever, and Tadashi doubted his little brother had much, or any, experience playing with himself back there. So he was tight as can be. On top of that, Tadashi wasn't an ideal starting size. In fact, he was about two and a half inches _bigger_ than the ideal starting size! Not to mention he'd thrust hard, driving his cock most of the way in on the first go instead of easing into Hiro slow and steady. 

But Hiro was in heat. His pain tolerance right now was through the roof, he had more than enough natural lubrication down there, and his body was actively working with Tadashi's to accept this gift of entry. So instead of crying from pain and pleading for Tadashi to stop, Hiro gave a pleased whine that reverberated loudly in the tile room, then pushed his ass back in an attempt to take the whole thing. 

"M-morrrrrree!" 

Outside his rut, Tadashi was tempted to pause just for a moment before properly taking Hiro. Even through the condom he'd felt a lovely flitting of pleasure that sucked the air from his lungs. But Tadashi didn't let himself stop. This wasn't for him, and this wasn't some romantic loving expression. This was about base instinct and needs. Hiro needed relief, even just enough to last them the way home. He had to provide. 

Tadashi started thrusting, going deep and fast. Hiro didn't bother to keep his voice down. He let loose with every moan, gasp, and cry he had. And he had a lot of them. Tadashi hoped the door was solid enough that the school staff wouldn't hear. While there wasn't technically anything majorly illegal happening- helping an Omega through their heat was common and often seen as necessary- it was against the rules to do it on school property and it was a minor misdemeanor to do it in public. Plus, natural as it was, it was still embarrassing, and the fact that they were blood brothers was... problematic. 

Still, there was no stifling to be had here. Hiro couldn't hold back like this, and Tadashi wasn't prepared to cover his mouth. But they were only getting louder. Tadashi was feeling pleasure, sure, but it was dampening through the condom and he found himself going harder and faster to try and increase it. The slap of skin on skin started to pair with Hiro's whines. And soon after, Tadashi's grunts joined both. 

Which made it extremely awkward when the bathroom door swung open. 

For the briefest of seconds, Tadashi heard the chatter of other students in the hallway outside. People milling about in the final minute before the school bell would ring again. Then the door closed. 

Tadashi froze, mid thrust and groan, and turned bright red as he heard footsteps echoing. There was no hiding, whoever it was had definitely heard he and Hiro, and there was no mistaking the sounds. But they said nothing, and simply walked into the stall right beside Hiro and Tadashi's, treading right on the discarded condom wrapper with what appeared to be combat boots. They didn't even bother to close their stall door before dropping their pants. A moment later the sound of piss hitting water filled the room. 

"Don't stop!" Hiro growled suddenly, jilting Tadashi. He stared in disbelief at his little brother, and gestured nonverbally and unnecessarily at the other stall.

"He clearly doesn't care!" Hiro said in a normal volume. Tadashi could have fainted. If it wasn't for the fact that during his past ruts he'd been horny enough to have acted the same way in this situation, he would have thought something was seriously wrong with his brother. 

Whoever was in the other stall made no sounds other than their continued urination to indicate their thoughts one way or the other. But Tadashi was far from reassured. As the school bell rang again, his mind started thinking over the worst possible outcomes. This student reporting him to the school, and the school reporting him and Hiro to the city. Even with a one day grace period, they could get into trouble for not filing, especially as siblings. Tadashi didn't want to think about what could happen following that. 

But Hiro wasn't going to let his brother stand there stunned, doing nothing. He huffed as the person in the next stall squeezed out their last few drops, then without warning tugged himself off of Tadashi's dick and spun around. 

"Fine, I'll do it!" 

Their cocks crossed, and Hiro's was smeared with some of his own slick from Tadashi's condom. He ignored it and pushed hard in the center of his brother's chest. Tadashi wasn't ready and was caught off-balance. He took a couple stumbling, steadying steps back before sinking onto the toilet seat again, right where Hiro wanted him. 

He quickly straddled his brother's waist before sliding back onto his cock. They both moaned, and the person in the next stall (who was clearly done with his business but sticking around for a performance anyway) chuckled. Tadashi wasn't sure if he'd heard the guy zip up! 

_Could... could he be jerking off to us?!_

As embarrassing, arousing, and important as the answer to that question was, Tadashi's attention was snagged by Hiro again when he started to bounce in his lap. Tadashi could feel every inch of his cock slipping out of his back door before plunging in again. Every bounce brought stars to his eyes. 

Neither of them was going to last for much longer. Both had essentially no experience, no stamina. Hiro was especially in danger of climaxing soon. He was young, in the throes of puberty, and on his cycle. Not to mention how impulsive and addicted to anything that gave him pleasure of any kind he was. But the boy kept bouncing away, letting Tadashi's dick slide out just shy of all the way, keeping only his cockhead inside, then sank back down the entire length as quickly as he could. 

The other guy chuckled again, then kicked his toilet handle to flush with his boot. Without saying a word he strode away to wash his hands. Hiro moaned louder and Tadashi almost wondered if it was on purpose, so the guy could hear him over the running water of the faucet and the rush of plumbing from the toilet. But Tadashi couldn't bring himself to deny his brother. He grabbed his hips and let the kid ride his cock. 

Tadashi leaned back, a little tense, when the other guy wolf-whistled and **finally** walked out of the bathroom. The halls outside were quiet and deserted now. Not a single voice to be heard from beyond the restroom door. 

"H-Hiro!" Tadashi gasped and tightened his hold on his brother's hips. "Hiro, that guy..."

"He's n-not telling anyone," the boy groaned, his cinnamon eyes rolling some (though from pleasure or exasperation Tadashi wasn't sure).

"B-but what if he does? We could end up in legal trouble! I don't-"

Hiro shut his brother up by kissing him again, deeper and much more fiercely this time. He blushed embarrassedly almost as soon as he did it. It felt like such a clichéd move! He was sure he'd seen people kiss to quiet someone at least a dozen times on Aunt Cass' various romcoms, He could have just covered Tadashi's mouth or something. But his gut and his heart had told him to kiss Tadashi, and he hadn't hesitated.

In his defense, his big brother did have really nice lips. Tadashi carried around a tube of Chapstick at all times, even in the summer, and applied it once an hour or so. The result was hard to argue with. But beyond just being warm and smooth, Tadashi's lips felt _right_. Hiro had heard before that kissing was how people tested for suitable partners. If it didn't feel right then you should move on, but if it fit, like his brother's did, then stick around. He wasn't sure how much stock he should put into that. Maybe it was just a myth? But if it was true, was Tadashi actually right for him? Or was his heat interfering and giving him the positive signals simply because he needed an Alpha?

Hiro took it as a good sign when Tadashi stole back a little control and deepened the kiss. He slid his left hand up the length of his brother's body from the hips and cupped his cheek, smiling against Hiro's mouth before he pressed Hiro up against him. The younger Hamada grabbed hold of his dick and began to frantically stroke himself off. His foreskin slid back to finally expose his pre-slicked and startlingly pink head. 

Hiro wished he could stay like this for longer, making out with his brother while riding his cock with fervent neediness. But he was getting close, and he needed his release badly. 

Well, what he needed was to be knotted. His body was _aching_ for it, base-driven for something it had never actually experienced. But he knew even without Tadashi having said anything that it wasn't going to happen this time. Tadashi was just helping out, and would be taking Hiro home as soon as he could. Being knotted would have delayed them by a solid twenty minutes at least. Plus, this was their first time, and Tadashi was already so nervous. Hiro knew him well enough to not expect the full treatment right away. All he needed was his own orgasm and he would be sated for maybe an hour. Of course, if he'd tried only masturbating then his orgasm would have relieved him for just around twenty minutes. There was something undeniably special about engaging with another person. 

Hiro broke the kiss, intending to warn his brother that he was getting close. But this coming climax was already promising to be intense. The swelling pleasure made it hard to think. Hiro barely managed to put out two discernable words of "Tadashi... gonna!" before his tongue grew too heavy and his breathing too thin and tight to speak any further. 

"Do it, Hiro!" Tadashi urged in an excited murmur. Evidently he could extrapolate what Hiro had meant. "You n-need this! Don't hold back."

The older boy began tracing two fingers down Hiro's spine. They rolled over an extremely sensitive spot at the base of his neck, a spot Hiro had never noticed before, and more pleasure than he'd ever experienced before shot through him. 

Hiro gave a real, proper howl with his toes curling and spine curving. Then he exploded all over his brother's chest with his cock, and drenched Tadashi's privates as a different spunk trickled from his rear with his climax. The boy could feel his drive and energy being sapped through the whole thing, as if his ejalculate held his spirit and was leaking it away. 

Hiro felt like his muscles, especially in his gut, were vibrating, were static. It was as if he were a spring doorstop. He'd been pulled to the side and held in place all day by fingers that were slowly slipping away. The anticipation of the inevitable springing had built and built, leaving him out of place and wanting, **needing** to go back to normal. And then Tadashi had fucked him. The spring slipped free as he came, and he was jarred but free and on the way to normalcy. 

Somehow Hiro kept bouncing through the blinding pleasure. Maybe he held some primal instinct to leave his Alpha satisfied? Or the ecstasy had shorted something temporarily so he stuck to his up-down-up-down pattern like a skipping record. Whatever the reason, it was good news for Tadashi. Sure, his little brother grew more sloppy while distracted by his arrival. He slowed somewhat, used his hips jerkily. But Tadashi hadn't needed much more. Just as Hiro started to come down and recover from his little death, Tadashi announced his. 

"It's happening! Hiro, servos [Placeholder] almighty! I c-can't believe I'm doing this in you!"

"Do it!" Hiro urged in a slurred, suddenly lethargic voice. "Please... I need it. Even without a knot and through a condom, my body can tell you're cummimg. I can feel it! And it'll help."

Tadashi didn't need to be asked. Even in his shocked disbelief he'd planned to keep going anyway. Sure, this was for Hiro (so he still told himself), but why let a perfectly good orgasm go to waste? 

In the last few seconds before it happened, Tadashi started thrusting up into Hiro. It was difficult in his seated and straddled position, but he was strong enough to manage. Besides, Hiro kept slowing and threatening to stop as his energy continued to fade. He needed the help. 

Tadashi hastily reached down between them and pinched the base of his cock tightly on either side in preparation. A good thing he acted when he did. From the split second before his first spurt shot out inside the condom, Tadashi was convinced this was the best orgasm of his life! If he'd tried to constrict his base even a second later, the signal wouldn't have reached his hand to make him move in time. His body was too absorbed in its own suddenly extreme pleasure. 

"AAAAHHH! Fuuuucckkk, H-Hiro!" 

He grunted and groaned louder than he'd allowed himself to be this whole time, enjoying his little brother's name on his tongue in this context. His cock was twitching and pulsing inside the boy, much to Hiro's barely muffled delight as he was still extra sensitive following his own climax. Tadashi felt his knot try to swell, but he kept holding the base of his dick to keep it from forming. Had he been rutting this would have been a useless attempt. Nothing short of a specialty ring-clamp would have denied it. But thankfully as he was cumming now, his fingers were sufficient. 

By the end, Tadashi wasn't sure how many times he'd shot into the condom. It had been several shots, but he hadn't bothered to count them. Still, he could tell from the weight at the tip and how the condom was sitting now that he'd expelled quite a lot. But when the high from sex started to fade, and he allowed himself to open his eyes and breathe, the clarity and shame sunk in. 

He was sticky from Hiro's spunk. It smeared his chest and stomach, already drying in the still air of their stall. It felt wrong on his skin. Wrong in an unhot way. Tadashi didn't regret what they'd done, but he couldn't help worrying if it was right or not. 

And Hiro... Tadashi gulped as he looked at the boy. His chest was heaving as he gulped down deep breaths, but his eyes were closed. Thankfully his skin was clear of cum, all of his load seemed to have leaked on Tadashi (god, and he could still smell it so strongly in the air). But Hiro was so young... just thirteen. In the eyes of many he was still a kid, even if he was set to graduate highschool with his older brother. 

_But he looks so cute... And he came onto me! It's not my fault, if we get in trouble. Except I'm not in rut. It was my decision, with no interference. And there's a witness out there somewhere..._

Hiro blinked open his eyes. They were heavily lidded with exhaustion, but they locked onto his older brother's before he smiled. 

"Thank you! I- um, that really helped, I think." 

His voice was only a murmur, a shadow of how he'd demanded and whined earlier. But just hearing Hiro talk and looking into his eyes helped settle Tadashi. He nodded and patted his brother's lower back. _Help Hiro now, deal later._

"Come on, hot stuff. Let's get you standing, and get our clothes back on. Preferably before someone else comes in." 

"Take me home?" Hiro asked in an innocent, tired voice as he struggled to lift himself off his brother's softening cock and onto his feet. He stretched and yawned then, unintentionally putting his sweaty body on display. 

Tadashi admired the curve of his brother's stretching features for a moment before coming back to his senses. 

"Yeah," he stood as well and ruffled Hiro's hair affectionately, "I'm taking you home."

**Notes for the Chapter:**

> Chapter Title Inspiration- Mercy by IAMX


	3. The Words and The Whispers

**Notes for the Chapter:**

> On a roll this week! And I'm seriously loving this fic. I might dive in more heavily after I post the next upcoming thing (a breakout one-shot for a fandom I've not written for before)

Tadashi wished they could have left for their home above the Lucky Cat Café immediately. He was tired, and Hiro looked about ready to pass out, but there were some obvious loose ends to tie up. 

Before getting to leave, they'd both dressed. Tadashi had removed and tied off his condom (Hiro eyed all the semen trapped inside covetously; it was an impressive amount for someone off their Cycle), grabbed Hiro's pad, and even snatched the condom wrapper from under the stall divider. He tossed all three, making sure to cover them in the trash can with paper towels soaked in soapy water to try and hide the scent as well as visual evidence. 

After that he'd used more damp paper towels to wipe clean the load Hiro had spilled on his front, donned his shirt, and offered his now fully-clothed brother a hand. He was glad when Hiro took it. He'd felt slightly worried that Hiro wouldn't accept any sort of adoring gesture, that he only wanted help relieving his sexual needs and wouldn't care for the emotional support Tadashi knew he'd also need, through his Heat and beyond. Of course, Tadashi didn't want to think of them as any sort of couple. There was already enough taboo surrounding brothers helping each other through their Cycles, and that was legal if done right. But a proper relationship would go too far in the eyes of many, probably in Hiro's as well. 

Still, he couldn't deny now that he definitely held an attraction to Hiro. It was confusing for sure, and made his head throb when he tried to think about it. But it was a curiosity to be explored and questioned another time. They were both tired and there were too many other things demanding attention for now. 

They'd left the school through the nearest exit at the end of the hall and walked to Tadashi's car, a small and blue used 2026 _Volte Face_. He wasn't worried about having left all his things in the classroom. The teacher would hold it for him, and he had a code to unlock the car doors and a fingerprint scanner instead of a key. Soon they were on their way home. 

Hiro passed out with his head resting on the window after only a couple of minutes. He gave adorable little snores that sounded too much like their cat, Mochi's, to not be the height of cuteness. Tadashi let him sleep. He certainly needed it. 

Once they arrived home, Tadashi had to carry his slumbering brother upstairs. They'd entered through the garage to sneak past the café, hoping to avoid the chatter and all eyes and noses. It was fairly easy for Tadashi to carry his brother, though. It felt like Hiro barely weighed anything. He seemed so small and innocent, and Tadashi couldn't stop staring at his sleeping face as they ascended. 

He was so wrapped up in Hiro's features that he almost didn't notice a hot wetness rubbing against his elbow. When he did, the hairs raised on his arms. He was holding Hiro under the knees and supporting the back of his neck bridal-style, and had brushed against the bottom of Hiro's shorts, against his butt. The seat of Hiro's shorts were now thoroughly soaked through!

He would have blushed, the thought of Hiro leaking slick clear through his clothing was undeniably a strange one, and he wasn't used to thinking about Hiro in a sexual light at all yet. But he could remember all the things he'd gone through at fifteen for his first Rut. How he'd bit down on his pillow in the dead of night to keep Hiro from hearing his whines as he humped and stained the bed. How he'd gone to Aunt Cass about it and she'd helped him pick out a toy to knot when he needed it, while he curled embarrassedly up against her on the couch (he didn't swing that way, but even with that and the embarrassment, his body had craved that physical touch). He wasn't about to judge Hiro for something the boy couldn't help. 

Hiro's eyes opened just a little bit when they reached the top of the staircase and stepped into their room. "You've got me?" He whispered. Tadashi gave him a reassuring smile. 

"Yeah, I've got you." 

Tadashi's bed was closer, so he deposited Hiro there. He wasn't worried about Hiro staining his bedding. It was likely he would, but Tadashi could change them later when needed. A minor inconvenience was worth it so his little brother could get some real rest.

"I know you need to really, properly sleep," Tadashi stroked the back of his hand soothingly down the left side of Hiro's cheek. "But we need to get you out of these sweat and slick-stained clothes first. Trust me, you'll feel much better and less icky naked."

"Are you just tryna...." Hiro trailed off tiredly and his suggestive smirk wavered and fell almost immediately, but it was obvious where he'd been going. 

"No, otōto. Not this time. I just want to help. Now come on, let's get you stripped."

Tadashi eased off Hiro's sneakers. They were tied a little loosely today, so he was able to remove them and Hiro's socks without having to undo the yellow laces. Hiro managed to sit up just long enough to shrug off his jacket and mostly slip out of his tank top before he fell back down and whined while starting to rub himself again.

"You need another suppressant, don't you?" Tadashi asked as he helped full Hiro's top the rest of the way off. 

"Th-the ones I took before only masked my scent," Hiro mumbled and closed his eyes again. 

"You also said Kyle got you a couple different kinds. Tell me where they are and I can find the right ones to help."

"Box," Hiro grunted, "u-und-der my bed." He spoke in a strained voice while he tried holding in a yawn. 

"I'll find it," Tadashi promised as he moved Hiro's hand off his crotch so he could unbutton and unzip him. The shorts and underwear slipped off easily, and Tadashi saw his little brother was fully erect again. He tried not to look at it, but restraint wasn't possible this time. Not fully, anyway. He watched with shallow breaths as Hiro wrapped a hand around himself and started to stroke off.

The poor boy didn't have enough energy to reach down and finger himself. That cock would give him minimal relief compared to what he needed. Still, the desperation from the futility had Tadashi breathing shallow and his hands shivering. It was impossible to not get hard with that show going on. 

And then the smell of slick leaked into the air again. It had been detectable since the duo had left school, but for a while Hiro's bottoms had withheld most of it, and even when it soaked through, they'd quickly gone inside where Tadashi couldn't smell as well thanks to his allergies and Mochi. Plus, Tadashi wasn't in Rut and they'd both been satisfied a little while before. It was wearing off fast, but it worked. 

But now with all of Hiro's clothes off and in their room that Tadashi did his best to keep fur-free, he could smell it all again. Fresh and strong on the air and pairing with the beginnings of the kid's initial pheromone release as his suppressant wore all the way off. Tadashi whined unconsciously and Hiro lifted his previously 10 mile gaze suddenly, looking hopeful and with a new light clicking on behind his irises. 

"Does this mean you'll mate with me again?!" 

He'd already asked, but Tadashi knew from his Omega Care course what to do. Repeat yourself and shut them down, then give them their suppressants if applicable. Thankfully, it was. Tadashi really didn't know how to handle Hiro without them. 

But it was indisputable that they both wanted it. He knew what to do, but his whole form ached to go against what was right. Tadashi shook his head fast and hard. He had to be responsible. Taking care of Hiro through his Heat meant a lot more than just sex. Besides, there were so many confusing emotions they would need to go through together, as well as safety talks. 

"I'm sorry, otōto. Not this time," Tadashi felt silly repeating himself. "Not yet. We both need rest, and you need care."

He didn't wait for Hiro's reaction. He straightened and made his way over to the cluttered opposite side of the room, through the divider. To Hiro's credit, Tadashi couldn't hear him complain, but he knew his brother wouldn't be able to help it soon. 

It was much darker in Hiro's space. Tadashi could still navigate it fairly well, but he went slowly because there were always surprises like wrenches and abandoned incomplete robotics projects strewn about. But once he made it to Hiro's bed he was able to grab a penlight from the bedside table. 

He tried to ignore the full sight of the mess when the light clicked on.

Focus!

He got on his hands and knees and stuck his head and shoulders beneath the bed. He shone the light around in search but was temporarily distracted. A slow and tired _pat....pat....pat..._

Hiro was masturbating more forcefully now. He still didn't have the energy to go at a helpful rate, and judging by his frustrated grunts the new forced strokes weren't enough to offset that. 

Tadashi did his best to tune it out and focused on the task at hand. He shined the light around, ignoring the sweets wrappers and underwear that had wound up kicked under there. He caught sight of a cardboard box that must have been what Hiro meant and grabbed it before quickly surfacing and dumping out the contents onto Hiro's bed. It was a mess of various things including a couple of extra slick pads and some bottles containing a few pills each. Tadashi snatched them up and carefully read the labels before setting two of them aside and going with the third. 

He almost grabbed another slick pad for Hiro, but thought better of it. These pills would hopefully be enough to regulate Hiro's Heat Cycle symptoms for a few hours, and the boy was already leaking on his bedding so he'd have to wash it either way. Plus, he'd heard tell that slick pads could be uncomfortable. Especially on younger Omegas, and especially during the first Cycle. Best to only use when absolutely necessary. 

And part of him didn't want to cover up the smell coming from the slick so soon.

Tadashi returned to his bed, with Hiro. The boy's hand now lay still on the bedding beside him. His gut was spattered with a pearly substance. There were a couple droplets on his fingers, too. It must have been a thoroughly unsatisfying orgasm; Omegas weren't designed to get much release that way during their Cycles, and he hadn't heard Hiro make any sounds when the boy had come. 

Tadashi sighed and walked the rest of the way over to set down the pill bottle, ignoring Hiro's needy whines as he drew near. The elder brother's lips quivered a little and his shoulders clenched as he was hit suddenly with a wave of empathy. Hiro didn't deserve his. He was still a kid in so many ways. And here he was, exhausted to the point of passing out from having his brother (of all people) in him earlier, but unable to actually rest because of his hormones. Tadashi knew the relief would come much quicker if he gave in and mated with his otōto again. It could be a quick one, too. But he held himself back this time. 

He pulled a tissue from a box on his shelf and started to clean the cum, which was growing clearer and thinner by the second, from Hiro's stomach. Hiro whined more at the contact and Tadashi's face smoldered. For the second time in about an hour he was cleaning Hiro up of semen. 

Hiro ignored the tissue Tadashi had and wiped the cum on his hand onto his brother's bedding. _Why not? That might as well happen. I'll have to wash my covers anyway, from his slick._

He tossed the tissue. Hiro's half-closed eyes then followed Tadashi as he circled the bed and bent down to open his mini-fridge and withdrew a bottle of water. He returned to Hiro's side and picked up the pill bottle again. 

"Here, you definitely need to drink something." He held out the water bottle. Hiro took it from him and began to sip weakly and eyed the pills distrustfully. Tadashi noticed. 

"And I looked through your pills and found the right suppressant for you to take. _EstrusBan._ " Tadashi grabbed the bottle again and twisted off the cap. 

"You're so young, you should take half a pill... But it looks like Kyle already thought of that, these have all been cut already!" He tipped one out in his hand and held it out to his brother. It was about a third the size of a dime, and faintly tinted yellow. 

Hiro shook his head. 

"Don't... Don't want pills," he said in a surprisingly normal voice. 

"yes you do, remember?" Tadashi scowled. "This will help you feel better, so you aren't so weak and horny anymore."

"You c-could fix it right now," Hiro's voice coaxed. "It'd be good for both of us."

_It would!_ spoke a voice in Tadashi's head. _You've already fucked him once today. He felt amazing, too. It won't change or hurt anything to go again. I bet he's so horny..._

_Stop it! He doesn't need that right now. He needs support. And for this moment, that's meds._

"Hiro, I can't. Not right now." 

"Why not? Are... are you never doing it with me again?" 

"I didn't say that. But you're not getting me to right now. If you want any freedom from what you're feeling, you'll take the pill." 

Hiro hesitated. 

"What... What's happening to me, Tadashi? I feel so tired... But I can't fall asleep!" 

"Your body knows that we had sex," the older brother explained, sitting down on his bed next to his little brother. "but it needs the knot, and it needs my, ah, jizz. Since it didn't get it, it's letting you know, nagging at you by making you feel drained. Just like when you're running low on anything else your body needs." 

"But what does-"

"Hiro," Tadashi cut across him, "listen. I promise we'll go over everything soon. You deserve answers and explanations. I have most of them. But you need to take your pill first. It should kick in pretty quick. that'll help with the exhaustion and help you fall asleep. When you wake up, we'll talk." 

The older boy moved the hand holding the pill forward a little more. Hiro looked at it for a moment, eyelids dipping so low. He rubbed his belly, maybe unconsciously, and shifted his weight a little so he could feel the slick on his bare butt that was soaking into the bedding. He snatched the half pill up and swallowed it down without even taking a sip, though he did finish off the bottle a little after. 

"Thank you." Tadashi ruffled his nude brother's hair while Hiro tossed the empty bottle, then grabbed his shoulder and gently pushed Hiro down. 

"You get some sleep," he began tugging up the comforter over Hiro's thin form. 

"'Dashi, will you sleep with me?" Hiro murmured, rolling onto his side and closing his eyes. Tadashi draped the comforter over the boy's shoulder. 

"Soon," he promised, rising. "I've got to do something first."

Hiro nodded and yawned, then rolled onto his side and closed his eyes. "Thank you. Goodnight."

"It's not goodnight yet," Tadashi chuckled. "Just a nap before dinner."

"Shhhhh, shut up, let me have this."

"Those pills must be fast-acting," Tadashi noted. " you sound more like your regular self, and you're falling asleep."

Hiro didn't answer, but Tadashi could tell by the way he was sniffing that he was still awake. It only took another minute for that to change, and Hiro's breathing became softer and more normal. 

Tadashi took a breath, deep and steeling, then grabbed his tablet off the bedside table. He could do this. As much as he wanted to wait, to hold off on involving anyone else for as long as possible, he knew it wouldn't be fair to Hiro. Even if his brother didn't realize it, they needed people who knew. 

So Tadashi turned the tablet on and opened a messaging app, clicking on a chat labeled **'AC.'** He started typing with trembling fingers. 

_I know you're busy with the café, but I needed to tell you something. Hiro started his first Heat. Please, don't worry! I've got it covered for now. A friend gave him suppressants and pads and stuff. We'll both be down for dinner and to talk later. I took him out of school, you'll have to call later and excuse our absences._

Tadashi hesitated. Inside, he was afraid to say too much, to admit to what had happened between him and Hiro. What if Aunt Cass wasn't supportive? What if she didn't understand, or got mad? But it would be worse if she found out later. And they needed to go about this legally. 

_I helped Hiro today. I don't want to go into it, but we'll need you to drive us to the courthouse tomorrow to file. In the meantime, we're upstairs and sleeping it off. When we wake up, I'm giving Hiro The Talk again and will walk him through everything. He can't be alone in this, he needs to have help. I have to do that for him._

He tried to reread everything he'd typed, make sure it was worded well and truthfully. He felt odd being so forward about it, but he was too tired to care. Tadashi pressed send and set the tablet back on the table. 

"All of this is for you," he whispered to his sleeping brother. "You're not going to be alone like I was. I promise."

He wasn't sure why he did it, but Tadashi started to strip. Losing his shirt, socks, everything but his underwear. He tried telling himself it was a closeness thing, not a sexual thing, but he couldn't be sure. 

Anticipation heavy on his heart, Tadashi slipped under the thin covers and wrapped his arms around Hiro. The kid shifted instinctively in his sleep and fit his naked body into the curve of Tadashi's. It was too comfortable. Tadashi didn't care if Hiro stained his crotch with slick, and he tried to let go of his worries. He let Hiro lull him to sleep. 

\---------------------------------  
\---------------------------------

Tadashi was woken up by three quick prods to his forehead. Three quick, annoying, mildly painful pokes, that is. 

"Gah! Whazzgoingon?" He blinked, then yipped and skirted back to avoid a fourth poke, nearly falling off the bed in the process. 

"Your stupid tablet was dinging," came Hiro's voice from the bedding next to Tadashi. The older boy blinked the sleep away, blurred shapes sharpening slowly. 

"It woke me up." 

"So you started poking my face? I think I was having a good dream..." 

Hiro reached forward to try and poke his brother one more time, but Tadashi managed to bat his hand away. 

"You haven't been asleep long enough to start dreaming," Hiro told him. "And actually, in my defense, I tried shaking you and saying your name a few times. You're normally such a light sleeper; that's why you usually catch me when I sneak out. I thought you were dead or something."

"You did not. But it's g-g-gooood to s-see you back to your normal, annoying self. The suppressant worked, I guess."

Tadashi yawned and stretched. He caught sight of the alarm clock on the bedside table. 6:47. He noted that the café had just closed. He also noticed that Hiro was wearing clothes now. 

_No._ he blinked. Not clothes. Just a shirt. Oversized. One of his! One of his simple, white SFIT tees. The school he hoped to get into after graduating. 

And honestly, it worked. Not in the way Hiro intended, maybe, but it worked. Tadashi wasn't currently horny (though you only needed eyes to notice this), so his thoughts were subject to change. But the way it covered Hiro's crotch so the first thing you saw looking down was his smooth thighs, and how baggy it was on his tiny form, reinforcing how small Hiro was next to his older brother.... it was just as sexy as Hiro in no clothes. 

The older boy swallowed, getting a grip on himself and redirecting his thoughts. 

"That's mine, isn't it?" Tadashi nodded at the shirt. 

Hiro shrugged. "I didn't think you'd mind. I felt exposed." 

"So you thought a shirt that doesn't fit you would work?" 

Hiro huffed defensively. "I'm wearing undies too!" He hitched up the shirt a little, just for a second before remembering he'd donned clothing because he felt too revealed. He covered himself again and looked away with pink cheeks. Tadashi had still gotten a fair look, though. They were one of his blue _LEGO_ patterned pairs, with a small bulge in front. Hiro still hadn't gotten new, more mature undies yet. He was too tiny for adult underwear, his waist and hips too slim. 

Tadashi realized that the pair also wasn't what he had stripped off him earlier. 

"So you woke up, tried to shake me awake, put on my top and walked across the room for your bottoms? And then poked me?"

Hiro cracked a small smile. "Hey, I already had the shirt. I only realized I wanted the underwear after I'd put it on. Why waste more effort?"

"Well, I'm pretty sure that was in my hamper," Tadashi pointed out. 

"Yeah, but it smells like you!" Hiro pouted. "Now are you gonna see why your tablet was dinging, or what?"

Tadashi bit his lip. It would be Aunt Cass messaging him back. He was worried about what she'd have to say. Telling her was the right thing, assuming she wasn't freaking out. If she was, he reasoned, she'd probably already be up here, yelling at he and Hiro. Still, the fear nagged. He wouldn't know for sure until he checked. 

"Pass me the tablet, please," he sighed. 

"Get it yourself," Hiro snorted. What a brat. 

"I'm naked!" Tadashi protested. "And it's on your side of the bed."

"You're wearing underwear."

Tadashi flushed. "You checked?" 

"Of course I did. How could I not?" Hiro crossed his arms and leaned back against the headboard. 

"I was sleeping, I'm your brother, and you thought I was naked and tried to sneak a look!" 

"Are you serious?" Hiro laughed. "We had sex, 'Dashi. And you slept with a naked me. We're well past that. It's not scandalous if I see you in your underwear, or if I see more."

"And yet you had to go put on underwear and my shirt," Tadashi pointed out. 

"Okay, I was also a little cold-" 

"Under the covers with me?" The older boy snorted. Hiro ignored him. 

"AND, are you really complaining that I'm not more naked as a defense for why you need to wear clothes around me?" 

Tadashi gaped at him. "I... That's twisting... They're different situations, really."

Hiro rolled his eyes. "Whatever, here's your tablet." He snatched it off the bedside table and held it out to his brother. 

"Thanks." 

He powered the tablet up. There was a string of notifications on the lock screen. Messages from Aunt Cass. Tadashi took a breath and began reading them. 

"Okay, Hiro. I told Cass everything." 

"You WHAT?!"

"I didn't go into any details. I just explained that I had to take care of it for you, and now you're on a suppressant. She was there for me when I started my Rut. Not in the way I was for you earlier, but still. She's progressive about this stuff. Besides, she had to take us to the courthouse tomorrow anyway."

Hiro frowned and pulled the covers up a little. "Why do we have to go there?" 

"To file a COMMA form... So our um, relationship, is legal. We have to within two days of us, well, fucking. It’s the law."

Hiro blushed, but looked his brother in the eye. "Why do we have to do that? Aren't those for a minor with an adult? You're only four years older than me."

"I'm not an adult yet, but you're my little brother, and you're younger than fifteen. Incest and boys your age.., even just one of those factors in a Heat or Rut-based relationship requires official filing. And I want to go about this the right way. I told Cass, so there's no going back. There's a record of it now, so she could get in trouble too if we don't file. And we need her signature on the forms, so she had to be told."

As he talked, Tadashi's voice went higher and higher. He sounded panicky. They both realized at the same time that he was every bit as freaked by the concept as Hiro was. Maybe even more so. 

"What did Cass say?" Hiro asked, thinking this would either bring about some relief if she was supportive, or rip off the bandaid if she wasn't. 

"She's okay with it," Tadashi said, looking back at the screen. "She says she's not mad, and of course she'll drive us tomorrow. And that she's glad I was there for you even if the situation isn't ideal. But she's going to talk to us both about it at dinner... Which is in ten minutes." 

Tadashi set the tablet aside. Honestly, that news didn't make him or Hiro feel any better or worse. They'd be able to breathe after the filing was over. 

"Until dinner, I want to talk with you. Brother to brother. I want you to ask me anything, so I can help. I know you must have questions."

Hiro sank down a little, putting his head back on the pillow and tugging the covers up to his chin.

"It's still pretty embarrassing and emotional stuff. And when you put me on the spot like this, all the questions I'd already thought up go rushing out of my head." 

"I get that," Tadashi grabbed Hiro's knee through the covers. He'd meant it as a caring and understanding gesture, but quickly realized it could be interpreted another way. A little anxiously, he froze up. He didn't want to pull away and seem like he thought touching Hiro was a mistake. But that just confused his suddenly nervous mind even more. 

To his surprise, Hiro slipped an arm out from under the covers and took Tadashi's hand. The older boy felt a mixture of relief and lurching arousal. Hiro's hand was so small, and surprisingly soft for a boy who liked working with mechanics. 

"I guess I have one question," Hiro admitted. Tadashi gulped and tried to clear his fuzzy head. 

"Yeah?" 

"Is this what you want? I know you said we have to file no matter what within 48 hours, but after we file... We could just give me suppressants when I'm on my Heat and you wouldn't have to 'help me.' Even though I'll want you to. But you're talking like we'll keep going." 

Tadashi had wondered if that would come up. Why have sex if suppressants do the job? Hell, he wasn't even sure if he had an answer to Hiro's other question, if he wanted to keep going. He liked it well enough. And there would come a time in just a couple of weeks where Hiro would be able to help him with his Rut (that was a thought for another time, though). But with all the pros, there were still complications. 

"I... I want to do whatever you want. But I'd prefer it if you told me when you're thinking straight. Not all juiced on hormones. Like when you're off your Cycle, or like now when you're on a suppressant. I mean, not right now, you should have time to think it ov-"

"I want it!" Hiro blurted out, squeezing Tadashi's hand. His declaration came with a look of sheepish hope. 

"Sorry, I just... I have thought about it. Some of it was while I was all horny, but I'm fine now. And I know I want this."

Tadashi wasn't sure what to say. It felt like his spirits were soaring while his heart sank. He wanted it too, but there was so much baggage connected to Hiro's Heat starting so early and them being blood brothers. 

Hiro sat up again, letting go of his brother's hand and emerging from the covers he'd just sought refuge in. He moved slowly, as if Tadashi were too fragile to handle sudden movements. He raised up a little on his knees, unintentionally hitching up his shirt and showing off those boyish undies again. 

Tadashi made himself look at his brother. Up and down his form, taking in his features. How he'd gone so long without noticing just how, he sought for the right word, _succulent_ Hiro was, he couldn't believe. But now that he had, he knew it was a certainty other Alphas and maybe even some of the rowdier Betas would, too. Probably had already, considering they didn't have the familial wall Tadashi'd had to climb. 

_He'll be safer from them with me... And I don't like what my Rut does to me. It's better to be in a consensual relationship with Hiro than to be driven mad by hormones and take things too far somewhere else._

"If you want this, I want this. We can conserve suppressants, save them for special circumstances like if I'm away, or you're having a really tough Cycle. And in the meantime I can- **we** \- can take care of each other." 

Hiro's eyes went full and warm. They looked like in cartoons when a character's eyes would shimmer, shiver, and shine with emotion. 

"Thank you! It... It means a lot. If you'd said no..." He trailed off. 

"What?" Tadashi sat up as well, exposing his bare chest, and reached up to touch his little brother's cheek. 

Hiro adopted a teasing voice. "Well, I'd have had to ask Kyle!" 

"Oh, shut up!" Tadashi laughed and pulled Hiro towards him. The boy came willingly, even tugging the bedding off Tadashi's lower half so he could straddle him properly. 

Their smiling lips met. Tadashi let Hiro lead, not wanting to overwhelm him. But the younger brother came at it with passion, pressing Tadashi back a little and groaning softly. His hips rolled down instinctively, making Tadashi extremely aware of his groin rubbing Hiro's butt through their underwear. 

Their bulges, one small and one large, stirred. Tadashi realized for the first time since waking up that he could still smell Hiro's slick and lingering pheromones on the air. He'd become so used to the scent in his sleep that, off his Cycle, he hadn't noticed until now, as he became aroused again. 

The kiss deepened. Hiro flicked his tongue across Tadashi's lips, and the elder Hamada sibling parted them eagerly, letting his brother in. He was getting harder and harder. He wanted to take Hiro again, then and there, in his own bed. It seemed like the thing to do. He had consent, obligation even. And judging by Hiro's tongue curling with his own, the boy's moans, his stiffening cock, and the movement of his hips grinding down onto Tadashi's hard-on, he was aroused too. 

But Tadashi pulled away, ending the kiss. He took a moment to catch his breath while Hiro looked at him with big, apprehensive eyes. 

"I'm s-sorry, Hiro. I want this. I want it really badly. Do you know how much it would mean to me, to do this with you while you're stable and I'm off my Cycle? A show of real trust and attraction. But... I told Cass we'd be down for dinner, and we only have a few more minutes to that." 

"We can't have a quickie?" Hiro pouted. He dropped his hands into his lap, which happened to be right by his brother's erection, and rubbed at his stiffy until their tips touched through their underwear.

Tadashi flushed. "That'd be... Quite the quickie. But really, we should stop here, pick things back up later. Your condoms are across the room, and we need to get dressed. Plus, if you get any more turned on than this... You might start, um, leaking again. Even with your suppressant active." 

Hiro bit his lip, but nodded. "I didn't think of that. You promise we'll do something later?"

Tadashi brushed a thumb over Hiro's lips. "I promise. If not tonight, then tomorrow. We're skipping school, after all, so we'll have plenty of time for ourselves!" 

"We are?" Hiro's eyes flashed excitedly. "Skipping school, I mean." 

"It's your first Heat," Tadashi explained." We've hardly worked out the kinks yet. This doesn't mean you'll always get off. F-from class, anyway. I can request your schoolwork sent here once we've found the rhythm."

"Shhhhh, don't ruin this for me," Hiro smirked. "Let me live in the fantasy a little bit longer." 

Tadashi gave an adoring eye-roll. 

"Okay, genius. But we need to get dressed now. I don't think it would send the right message if we went to dinner in our underwear." 

"Can I at least keep the shirt?" Hiro started to obediently dismount from his brother, and climbed out of bed entirely. 

"Ummmm.... You can _borrow_ one of my clean shirts, if you insist on wearing my clothes, but let's throw that one back in the hamper where it belongs."

**Notes for the Chapter:**

> Chapter Title Inspiration- Mercy by IAMX

**Author's Note:**

> Sorry, I know that's a sucky cutoff. I wanted chapter one to be simple. The next couple will induct new characters and more dynamics from the Omegaverse. . . And sex. Lots of hot, sticky sex
> 
> If you're anything like me, there's probably a couple things in this chapter that made you go "huh??" I promise they'll be explained in the next chapter
> 
> I'm now a member of SCAR! They seem like a really good organization for more taboo fic writers here on AO3. And a great support system for the writing process  
> https://tiny.cc/NI0W4
> 
> Work Title Inspiration- Mercy by IAMX


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